Single photoionization with excitation and double photoionization of He endofullerenes

Recently, using a non-perturbative time-dependent close-coupling (TDCC) method we investigated and confirmed the existence of these resonances in the double photoionization cross section of He@C$_{60}$ [1, 2]. Here, we extend our previous studies to examine confinement resonances not only in the double photoionization process, but in the process of single photoionization with~excitation for various He endofullerenes, namely He@C$_{36}$, He@C$_{60}$ and He@C$_{82}$. We found He@C$_{82}$ also displays confinement resonances in the double~photoionization cross sections; while for He@C$_{36}$ the confinement resonances are suppressed. For single photoionization leaving the He$^{+}$ ion in its ground state, we found the magnitude of the cross sections for the endofullerenes is comparable to that of helium. For single photoionization with excitation to the n=2 shell, the endofullerene cross sections showed a~reduction as compared to bare He atoms; while for photoionization with excitation to the n=3 shell, the cross sections for the endofullerenes showed an enhancement. In addition, we also found confinement resonances in the single photoionization with excitation cross sections.\\[4pt] [1] J A Ludlow, T-G Lee, and M S Pindzola, Phys. Rev. A 81, 023407 (2010)\\[0pt] [2] J A Ludlow, T-G Lee and M S Pindzola, J. Phys. B: At. Mol. Opt. Phys. 43 235202 (2010)